The human channel gating-modifying A749G CACNA1D (Cav1.3) variant induces a neurodevelopmental syndrome-like
Nadine J Ortner1, Anupam Sah1, Enrica Paradiso2
1Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria.
Abstract:
Germline de novo missense variants of the CACNA1D gene, encoding the pore-forming α1 subunit of Cav1.3 L-type Ca2+ channels (LTCCs), have been found in patients with neurodevelopmental and endocrine dysfunction, but their disease-causing potential is unproven. These variants alter channel gating, enabling enhanced Cav1.3 activity, suggesting Cav1.3 inhibition as a potential therapeutic option. Here we provide proof of the disease-causing nature of such gating-modifying CACNA1D variants using mice (Cav1.3AG) containing the A749G variant reported de novo in a patient with autism spectrum disorder (ASD) and intellectual impairment. In heterozygous mutants, native LTCC currents in adrenal chromaffin cells exhibited gating changes as predicted from heterologous expression. The A749G mutation induced aberrant excitability of dorsomedial striatum-projecting substantia nigra dopamine neurons and medium spiny neurons in the dorsal striatum. The phenotype observed in heterozygous mutants reproduced many of the abnormalities described within the human disease spectrum, including developmental delay, social deficit, and pronounced hyperactivity without major changes in gross neuroanatomy. Despite an approximately 7-fold higher sensitivity of A749G-containing channels to the LTCC inhibitor isradipine, oral pretreatment over 2 days did not rescue the hyperlocomotion. Cav1.3AG mice confirm the pathogenicity of the A749G variant and point toward a pathogenetic role of altered signaling in the dopamine midbrain system.
Insights
Germline variants in CACNA1D, affecting Cav1.3 L-type Ca2+ channels (LTCCs), are linked to neurodevelopmental disorders. This study confirms the pathogenicity of the A749G variant using a mouse model, revealing altered dopamine neuron activity.
Area of Science:
- Neuroscience
- Genetics
- Pharmacology
Background:
- Germline de novo missense variants in CACNA1D, encoding Cav1.3 L-type Ca2+ channels (LTCCs), are associated with neurodevelopmental and endocrine disorders.
- These variants are hypothesized to enhance Cav1.3 channel activity by altering gating properties, suggesting LTCC inhibition as a therapeutic strategy.
- The pathogenic role of these gating-modifying CACNA1D variants remains unproven in vivo.
Purpose of the Study:
- To provide in vivo evidence for the disease-causing potential of gating-modifying CACNA1D variants.
- To investigate the functional consequences of the A749G CACNA1D variant in a mouse model.
- To explore the role of altered Cav1.3 channel activity in neurodevelopmental phenotypes.
Main Methods:
- Generation of Cav1.3AG mice harboring the A749G variant, identified in a patient with autism spectrum disorder (ASD) and intellectual impairment.
- Electrophysiological recordings in adrenal chromaffin cells and dopamine neurons from heterozygous mutant mice.
- Behavioral analysis of mutant mice to assess neurodevelopmental abnormalities, including social behavior and locomotion.
Main Results:
- Heterozygous Cav1.3AG mice exhibited LTCC gating changes in adrenal chromaffin cells consistent with heterologous expression studies.
- The A749G mutation led to aberrant excitability in substantia nigra dopamine neurons and dorsal striatum medium spiny neurons.
- Mutant mice displayed phenotypes mirroring human disease spectrum, including developmental delay, social deficits, and hyperactivity, without significant gross neuroanatomical changes.
- Despite increased sensitivity to isradipine, LTCC inhibition did not rescue hyperlocomotion in mutant mice.
Conclusions:
- The A749G CACNA1D variant is pathogenic, confirming the disease-causing potential of gating-modifying variants.
- Altered signaling in the dopamine midbrain system is implicated in the pathogenesis of neurodevelopmental disorders associated with CACNA1D variants.
- Cav1.3 LTCCs represent a potential therapeutic target, although direct inhibition may not fully rescue observed behavioral phenotypes.
